1. Field of the Invention
The inventions disclosed and taught herein relate generally to methods and apparatuses for sulfiding a hydrocarbon processing catalyst; and more specifically to methods and apparatuses for sulfiding a hydrocarbon processing catalyst resident in a reactor.
2. Description of the Related Art
Hydroprocessing units, such as hydrotreaters, hydrodesulfurizers and hydrocrackers, found in hydrocarbon refineries utilize metal catalysts to aid the chemical reactions. These catalysts require periodic sulfiding to reach maximum catalytic activity. For purposes of this disclosure, “sulfiding” means causing the reaction of a catalyst metal with hydrogen sulfide.
There are several ways to sulfide catalyst already packed in a reactor vessel, commonly referred to as in-situ sulfiding, such as by using the naturally occurring sulfur in the hydrocarbon feed stock (aka sour feed). While avoiding the cost of an independent source of sulfur, using feedstock sulfur can be time consuming and potentially harmful if the sulfur content is not carefully monitored or high enough. An alternative to using feedstock sulfur is to use an independent sulfur source such as mercaptans, sulphides, disulphides, polysulphides and sulfoxides, such as Dimethyl Disulfide (DMDS), Dimethyl Sulfide (DMS), Dimethyl Sulfoxide (DMSO), di-tertiary-butyl polysulfide (TBPS), tertiary nonylpolysulfide (TNPS) and refinery acid gas. These sulfur sources can be used to perform in-situ liquid phase sulfiding or in-situ gas phase sulfiding.
In general, within the hydroprocessing unit, sulfur is reacted with hydrogen to form hydrogen sulfide (H2S). The metal oxide catalysts are reacted with hydrogen sulfide (H2S) and hydrogen (H2) at elevated temperatures to form the active metal sulfide, such as MoS2, CO9S8, WS2 or Ni3S2, in an exothermic reaction. Theoretically, only the stoichiometric amount of sulfur is needed to activate the catalyst. However, in the real world of commercial refineries, it is common to use more than the stoichiometric amount of sulfur to ensure complete sulfiding. Excess sulfur creates excess hydrogen sulfide and other sulfiding products that must be disposed of or otherwise dealt with.
Liquid DMDS is often used as the sulfur source because of its high sulfur density by weight (compared to the other potential sulfur sources) and lack of solid or overly reactive decomposition products, which absence reduces coking. DMDS can be injected into the hydrocarbon feed stream as a liquid or into the hydrogen recycle loop as a gas. Under temperature and pressure, DMDS will decompose into H2S at several temperature ranges including about 350° F. to about 450° F.; about 390° F. to about 500° F. and about 450° F. to about 520° F.
The inventions disclosed and taught herein are directed to methods and apparatuses for efficiently sulfiding catalysts packed in a reactor vessel.